The present invention relates generally to nuclear medicine, and, more specifically, to a camera for detecting shallow lesions or tumors identified by a radioactive agent.
Diagnostic imaging with photons (i.e. X-rays or gamma rays) is divided into two categories: Transmission and emission. In transmission imaging, such as common x-ray imaging, the examination site such as the chest is positioned close to or adjacent to a flat x-ray film plate assembly. A suitable point x-ray source is temporarily provided behind the patient so that x-rays pass through the patient to the film plate. The film plate typically includes a rigid frame in which is supported a flat photographic film with one or two conventional scintillation screens which emit light when bombarded with x-rays for forming an exposure image on the film. The film is conventionally developed so that the recorded image may be visually analyzed by a radiologist to determine whether or not there is an abnormality such as a tumor or other lesion therein.
On the other hand, nuclear radiation is used for detecting various anomalies within the human body through emission of gamma rays from the body. In this method, a gamma-emitting radioactive isotope in a pharmaceutical agent is administered to the patient either orally or by injection, with the agent being specifically selected for targeting a selected organ or lesion such as a cancerous tumor in the eye, thyroid, or trunk, for example. The patient then lies down on a table or sits down in a chair in front of a gamma camera which detects the gamma radiation from the patient, or more particularly from the examination site of interest in the patient, analyzes the data, and provides an analysis in the form of a computer produced digital image of the radiation source. In this way location and configuration of the tumor may be identified in the patient. The gamma camera is typically quite large and heavy, and is used for a relatively short time on the order of tens of minutes to provide accurate and detailed quantitative data regarding the tumor.
Unlike the simple chest x-ray, conventional gamma cameras use sophisticated radiation detector heads having suitable scintillators therein and corresponding photomultiplier arrays for creating the electrical signals or pulses from the radiation emitted from the examination site. These signal or pulses are then analyzed mathematically using high-speed processors so that a virtual image of the source distribution will be produced. Emission imaging is also done in the tomography mode, in which multiple gamma cameras rotate around the patient.